IntroductionThe first BMW M3 Convertible debuted at the Frankfurt Motor Show in 1985. Based on the race-bred 4-cylinder engine E30-platform M3 Coupe, but with a convertible soft top, it was a limited Europe-only release. The second-generation E36-platform M3 Convertible was finally released to North America in 1998, followed by the third-generation E46-platform M3 Convertible in 2001. With each subsequent generation, the M3 Convertible grew in size, weight and horsepower as luxury items, technological improvements, and safety advancements were applied to the newer platforms.

The all-new M3 convertible, now in its fourth generation, is based on the current E93 platform. It is the first M3 Convertible with a power-operated retractable steel hardtop, available M double-clutch gearbox, and a standard 8-cylinder powerplant. Compared to its predecessors, the 2008 M3 Convertible is more refined, more luxurious, and faster, according to BMW.

Model LineupAt first glance, the 2008 BMW M3 Convertible appears nearly identical to the M3 Coup_-except for its convertible roof.Like the M3 Coup_, the M3 Convertible only shares the two doors, trunk lid, windows and headlights with the standard 3 Series Convertible. All other body components are M3-specific. Every M3 Convertible model is equipped with the same 8-cylinder powerplant, suspension and seating configuration.

There is no mistaking an M3 Convertible. The aluminum hood sports a striking power dome, and the front quarter panels have distinctive M-style side "gills" just below the model-specific aerodynamic mirrors. The rear of the M3 sports a dual twin-pipe tuned exhaust. Standard aluminum wheels are 18 inches in diameter, with forged light-alloy 19-inch wheels optional. The convertible top is a 3-piece lightweight steel structure with an integrated heated glass window. It is fully automatic in its opening and closing function: a process that takes about 22 seconds and can be activated via remote control. With the roof open the M3 Convertible affords 7.35 cubic feet of storage space: enough to accommodate two golf bags, according to BMW.

The interior of the M3 Convertible is designed for maximum driving pleasure. Instruments are white-illuminated, with red needles, and feature a variable engine-speed warning range based on engine temperature. M-model-specific seats, leather-clad steering wheel, and shift knob offer additional bolstering, comfort and control for spirited driving. Unique to the M3 Convertible, the leather upholstery features BMW's Sun Reflective Technology on the surfaces. Special cooling pigments integrated into the material reduce surface heating by nearly 70 degrees on sunny and hot days, BMW says. Even the air conditioning has been adapted for open-top use: A special "convertible mode" puts the automatic climate control into a special program that establishes proper vent temperature based on the temperature of the air and the intensity of the sunlight outside the vehicle.

HardwareAs is customary, the 2008 M3 Convertible is built on a traditional front-engine, rear-wheel-drive platform. The 4.0-liter V-8 engine is rated at 420 hp, making this the most powerful M3 Convertible ever sold. While excess weight is often a problem with 8-cylinder engines, BMW engineers went to great lengths to ensure purists need not worry: The new V-8 powerplant weighs 33 pounds less than the inline 6-cylinder powerplant it replaces. The standard transmission is a 6-speed manual with a mass inertia optimized, and internally ventilated, twin-disc clutch. An all-new 7-speed double-clutch gearbox ("M DCT"), with 11 electronically controlled driving programs, is also available. According to BMW, a 0-60-mph sprint in the M3 Convertible will take just 5.3 seconds. Top speed is electronically limited to 155 mph.

The chassis of the 2008 BMW M3 Convertible is nearly perfectly balanced front to back, and the fully independent suspension has been entirely revised and reinforced for optimal handling in the slightly heavier convertible chassis, according to BMW. Nearly all of the components are cast or forged in aluminum. The spring/strut front axle works in conjunction with the reinforced front strut-tower bar to keep the front wheels in an optimal position during maneuvers. The rear axle, a 5-arm design, is also reinforced with a V-strut under the chassis. Electronic Damper Control (EDC) optimizes the car's dive and roll during cornering, acceleration and braking. Power distribution between the wheels is controlled both mechanically and electronically. Mechanically, the M Differential Lock is able to transfer 100 percent of the power to the drive wheel with the best traction. Electronic intervention, which can be completely defeated, is handled by the multi-mode Dynamic Stability Control (DSC). The M3 Convertible features four ventilated, drilled, compound high-performance anti-lock disc brakes.

SafetySafety and performance are not mutually exclusive on the 2008 BMW M3 Convertible. Dual front-impact air bags (with dual-threshold deployment), front-seat side-impact air bags, and pre-tensioning seat belts help protect the driver and front passenger from crash injuries. The M3 Convertible is also equipped with a rollover sensor system that permanently monitors the vertical and horizontal movements of the vehicle.If the system determines that a rollover is imminent, safety roll bars positioned behind the rear headrests pop up immediately to limit the danger to occupants, BMW claims. As a further precaution against rollover injuries, the A-pillars and windscreen frame are reinforced on the M3 Convertible model. BMW's Advanced Crash Safety Management system will unlock doors, switch on hazard flashers and interior lights, and disconnect the fuel pump, alternator and starter in the event of a severe accident.

The 2008 M3 Convertible may also be equipped with BMW Assist, a hands-free communication system based on GPS and cellular phone technology. In the event of an accident, the system will automatically alert authorities to the exact location of the vehicle. BMW Assist can also be used for roadside assistance, stolen vehicle recovery and concierge services.

TechnologyBMW claims to have introduced the world's first 7-speed double-clutch gearbox conceived and developed for a high-speed power unit. Replacing BMW's sequential manual gearbox (SMG), it employs dual oil-cooled wet clutches. One of the clutches is used for the even gears; the other is reserved for the odd gears and reverse gear. While one clutch is in use, the other stands ready for lightning-fast gear changes. The transmission is controlled by a computer that adjusts engine output and speed for optimal shifting speed and smoothness under nearly every driving condition. The driver is able to select one of 11 shift programs to let the transmission work in automatic or manual mode. While automatic mode requires no driver input, the manual mode allows the operator the option to shift gears with the sport selector lever or paddles mounted on the steering wheel. The innovative new transmission is designed to operate at engine speeds of 9000 rpm (with the M3 Convertible redlining at 8400 rpm). Not only is the new double-clutch gearbox faster than a manual transmission and a conventional converter-type automatic transmission, BMW says it also delivers better fuel economy and reduced emissions.-Michael Harley